The Electronic Privacy Information Center filed its complaint with the Federal Trade Commission just days after Google Inc. altered the service to address mounting privacy concerns.

Since launching Google Buzz as part of Gmail a week ago, the search company has come under fire for automatically creating public circles of friends for users based on their most frequent Gmail contacts. Over the weekend, Google altered the service to merely suggest contacts for its users’ social networks.

Despite the changes, EPIC argues that privacy violations remain because Google automatically signs up Gmail users for Buzz, rather than waiting for them to do so themselves, or “opt in” for the service. EPIC wants the FTC to require Google to make Buzz a “fully opt-in” service. It also wants the company barred from using Gmail address book contacts to compile social networking lists.

“This is a significant breach of consumers’ expectations of privacy,” EPIC Executive Director Marc Rotenberg said in a statement. “Google should not be allowed to push users’ personal information into a social network they never requested.”

But Google insists that it gives users control because, even though it adds a “Buzz” link to all Gmail accounts, users must click on the link and agree to activate the service. Google also gives users the option to disable Buzz.

In response to the EPIC complaint, Google said it has already made some changes to Buzz based on user feedback and has “more improvements in the works.”

“We look forward to hearing more suggestions and will continue to improve the Buzz experience with user transparency and control top of mind,” the company said.